Environmentally sustainable management of dairies is critical to the economic health of American agriculture. A major upcoming challenge is the planning, implementation, and documentation of nutrient management practices for proposed federal regulations for concentrated animal feeding operations (CAFO, EPA 2008) to control water pollution. The present invention is focused on dairy waste management and on developing improved dairy waste management methods that will help to ensure that impacts on groundwater quality are minimized.
Applying dairy manure and wastewater to agricultural fields has been shown to increase crop yields, improve water holding capacity of the soil and enhance soil fertility, “Estimation of N and P in Florida Dairy Wastewater for Silage Systems”; Gallaher, R. N., et al., Presented at the 31st Florida Dairy Production Conference, Gainesville, Fla., April 1994. However, when manure wastes are applied to fields at high rates over a period of years, nutrients can accumulate causing eutrophication (excessive growth of aquatic plants and subsequent decay caused by increased phosphorus and nitrogen concentrations) in drainage waterways; degradation of drinking water; nutrient toxicities or nutrient deficiencies in plants; disruptions in soil microbial populations; and nutritional imbalances for grazing animals, “Soil Facts. Dairy Manure as a Fertilizer Source” North Carolina Cooperative Extension Service, AG-439-28.
Growers and dairy producers also run the risk of violating state and federal regulations designed to avoid these issues.
Ferric oxide hydroxide (FeO(OH)) is routinely used in aquaria to scavenge phosphate. Formulations of this material are available from Ocean's Blend and other vendors. It is assumed that there is an exchange between hydroxyl groups and inorganic phosphate whereby both soluble and insoluble forms of ferric ion wherein two or more of the plus charges of the three charges characterizing ferric ion are neutralized by phosphate. The resulting solid forms of product are susceptible to bacterial degradation to again release the phosphate, although at a relatively slow rate.
Zeolites (which can be of the class of crystalline compounds known as aluminum silicates, zirconium silicates and the like) and some ceramics have been used to remove ammonium and/or ammonia from wastewaters. See, for example, Cooney, E. L., et al., Separation Science & Technology (1999) 34:2741-2760. This, too, has been used extensively in aquaculture.
Zeolites are also known to remove various heavy metals, including ferrous ion (Fe+2) from aqueous environments. For example, Lenntech BV (Delft, The Netherlands) lists the capacity of zeolite to be in the range of about 1 mEq/g for Fe+2, Zn+2, Ni+2, Cd+2, Pb+2, and Cu+2 in that order of affinity. In general, this is understood as a cation exchange process for heavy metal binding but it is not heavy metal specific.
There is still a need, however, for an efficient system to remove, both phosphate and ammonia from areas of agricultural waste. For example, the concentrations of these ions permitted in lagoons used to store waste from dairy cows places limits on the number of cows that can be maintained in a herd. Many of these lagoons are quite large, exceeding the area of a football field. An efficient method to convert the phosphate and ammonium ions into forms that can be recovered and used as fertilizer would permit larger herds to be maintained. The present invention provides composites to achieve this end through the production and use of a bifunctional binding zeolite.